1. Field of the Invention
The present invention relates to a method of producing a cooling fan attached type heat sink used in an electronic component cooling apparatus for cooling electronic components such as a MPU (micro processor unit).
2. Description of the Related Art
FIGS. 5 and 6 are a plan view and a side view of an electronic component cooling apparatus using a conventional general cooling fan attached type heat sink marketed and manufactured by the present applicant. This electronic component cooling apparatus is pending for patent under the publication No. JP-A 10-86491 (1998) (U.S. patent application Ser. No. 09/190,872). As shown in FIGS. 5 and 6, this electronic component cooling apparatus consists of combination of a heat sink 101 and a cooling fan 102. The heat sink (cooling fan attached type heat sink) 101 attached to the cooling fan 102 comprises a base 103 to which an electronic component is to be mounted, a plurality of radiating fins 104 provided for the base 103 and a fan case engagement portion 106 for engagement with a fan case 105 of the cooling fan 102. In this example, the cooling fan attached type heat sink 101 is formed by subjecting an extrusion obtained by extrusion molding to cutting or punching work. Heat sinks used for this type of electronic component cooling apparatus are sometimes formed by casting or forging depending on their shapes.
In a cooling fan attached type heat sink, it is desired to increase the number of plural radiating fins and thereby improve the radiating effect without hindering miniaturization of the heat sink. However, in addressing such desires, the ratio of the height H of the radiating fins with respect to the interval dimension G between neighboring radiating fins (tong ratio: H/G) becomes large, which makes molding, for instance, by extrusion molding difficult. Particularly, when the tong ratio is more than or equal to 10, it is impossible to form the plurality of radiating fins by extrusion molding. Moreover, there are limitations for shapes of the radiating fins that can be formed by casting and forging.
It is an object of the invention to provide a method of producing a cooling fan attached type heat sink with a plurality of radiating fins having a shape that is difficult to be formed or cannot be formed by casting, forging or extrusion molding with low costs and with relative ease.
In one aspect, the present invention aims at improving a method of producing a cooling fan attached type heat sink comprising a base, a plurality of radiating fins provided for the base and a fan case engagement portion for engagement with a fan case of a cooling fan for forcefully cooling the base. According to the present invention, at first, a heat sink preform having a base, a fan case engagement portion and a radiating fin formation portion in which a plurality of radiating fins are to be formed is integrally formed by casting, forging or extrusion molding. Next, a plurality of radiating fins having such a shape that is difficult to be formed or cannot be formed by casting, forging or extrusion molding or having a large tong ratio is formed by subjecting the radiating fin formation portion to cutting work.
In the cutting work step, the cutting work can be effected so that a tong ratio that is defined as a ratio of the height of the radiating fins with respect to the interval dimension of neighboring radiating fins is more than or equal to 10.
Further, the heat sink preform can be formed of metals having high heat conductivity such as aluminum, copper and the like.
In another aspect, the present invention aims at improving a method of producing a cooling fan attached type heat sink comprising a base, a plurality of radiating fins provided for the base and a fan case engagement portion for engagement with a fan case of a cooling fan for forcefully cooling the base. The present invention comprises the steps of: forming a heat sink preform by casting, forging or extrusion molding, the preform having a base, a fan case engagement portion and a fin fixation portion to which a plurality of radiating fins is to be fixed; and fixing a plurality of radiating fins having such a shape that is difficult to be formed or cannot be formed by casting, forging or extrusion molding or having a large tong ratio to the fin fixation portion of the heat sink preform.
The plurality of radiating fins can be configured as a radiating fin unit in which any two neighboring radiating fins of the plurality of radiating fins arranged side by side are connected via a connecting portion.
The radiating fin unit can be integrally formed of a material having a heat conductivity higher than that of the heat sink preform.
In the fin fixation portion of the heat sink preform is provided a plurality of positioning grooves for positioning the radiating fin unit, so that it is possible to fix the radiating fin unit to the fin fixation portion with the plurality of connecting portions located on one side of the radiating fin unit being fitted into the plurality of positioning grooves.